Shaw Wei D Tsen

Enhancing DNA Vaccine Potency by Modifying the Properties of Antigen-Presenting Cells

DNA vaccines represent a potentially promising approach for antigen-specific immunotherapy. Advances in our knowledge of the adaptive immune system have indicated that professional antigen-presenting cells, especially dendritic cells (DCs), play a key role in the generation of antigen-specific immune responses. Thus, the modification of the properties of DCs represents an important strategy for enhancing the potency of DNA vaccines. This review discusses strategies to increase the number of antigen-expressing DCs, enhance antigen expression, processing and presentation in DCs, promote the activation and function of DCs, and improve DC and T-cell interaction, in order to optimize DNA vaccine-elicited immune responses. Continuing progress in our understanding of DC and T-cell biology serves as a foundation for further improvement of DNA vaccine potency, which may lead to future clinical applications of DNA vaccines for the control of infectious diseases and malignancies.

Selective inactivation of micro-organisms with near-infrared femtosecond laser pulses

We demonstrate an unconventional and revolutionary method for selective inactivation of micro-organisms by using near-infrared femtosecond laser pulses. We show that if the wavelength and pulse width of the excitation femtosecond laser are appropriately selected, there exists a window in power density that enables us to achieve selective inactivation of target viruses and bacteria without causing cytotoxicity in mammalian cells. This strategy targets the mechanical (vibrational) properties of micro-organisms, and thus its antimicrobial efficacy is likely unaffected by genetic mutation in the micro-organisms. Such a method may be effective against a wide variety of drug resistant micro-organisms and has broad implications in disinfection as well as in the development of novel treatments for viral and bacterial pathogens.

Therapeutic HPV DNA vaccines.

Human papillomavirus (HPV) has been associated with several human cancers, including cervical cancer, vulvar cancer, vaginal and anal cancer, and a subset of head and neck cancers. The identification of HPV as an etiological factor for HPV-associated malignancies creates the opportunity for the control of these cancers through vaccination. Currently, the preventive HPV vaccine using HPV virus-like particles has been proven to be safe and highly effective. However, this preventive vaccine does not have therapeutic effects, and a significant number of people have established HPV infection and HPV-associated lesions. Therefore, it is necessary to develop therapeutic HPV vaccines to facilitate the control of HPV-associated malignancies and their precursor lesions. Among the various forms of therapeutic HPV vaccines, DNA vaccines have emerged as a potentially promising approach for vaccine development due to their safety profile, ease of preparation and stability. However, since DNA does not have the intrinsic ability to amplify or spread in transfected cells like viral vectors, DNA vaccines can have limited immunogenicity. Therefore, it is important to develop innovative strategies to improve DNA vaccine potency. Since dendritic cells (DCs) are key players in the generation of antigen-specific immune responses, it is important to develop innovative strategies to modify the properties of the DNA-transfected DCs. These strategies include increasing the number of antigen-expressing/antigen-loaded DCs, improving antigen processing and presentation in DCs, and enhancing the interaction between DCs and T cells. Many of the studies on DNA vaccines have been performed on preclinical models. Encouraging results from impressive preclinical studies have led to several clinical trials.

Inactivation of viruses by coherent excitations with a low power visible femtosecond laser.

BackgroundResonant microwave absorption has been proposed in the literature to excite the vibrational states of microorganisms in an attempt to destroy them. But it is extremely difficult to transfer microwave excitation energy to the vibrational energy of microorganisms due to severe absorption of water in this spectral range. We demonstrate for the first time that, by using a visible femtosecond laser, it is effective to inactivate viruses such as bacteriophage M13 through impulsive stimulated Raman scattering.Results and discussionBy using a very low power (as low as 0.5 nj/pulse) visible femtosecond laser having a wavelength of 425 nm and a pulse width of 100 fs, we show that M13 phages were inactivated when the laser power density was greater than or equal to 50 MW/cm2. The inactivation of M13 phages was determined by plaque counts and had been found to depend on the pulse width as well as power density of the excitation laser.ConclusionOur experimental findings lay down the foundation for an innovative new strategy of using a very low power visible femtosecond laser to selectively inactivate viruses and other microorganisms while leaving sensitive materials unharmed by manipulating and controlling with the femtosecond laser system.

Inactivation of viruses by laser-driven coherent excitations via impulsive stimulated Raman scattering process

The inactivation of viruses such as M13 bacteriophages subject to excitations by a very low power visible femtosecond laser has been studied. Our experimental results show that for a visible femtosecond laser having lambda = 425 nm and a pulse width of 100 fs, the M13 bacteriophages are inactivated when the laser power density is greater than or equal to 49 MW/cm(2). The medium lethal laser power density (LD(50)) is 51.94+/-0.14 MW/cm(2). The functionality of M13 bacteriophages has been shown to be critically dependent on the pulse width as well as power density of the excitation laser. Our work demonstrates that by using a very low power visible femtosecond laser, it is plausible to inactivate viruses such as the M13 bacteriophages through impulsive stimulated Raman scattering process. These experimental findings suggest a novel avenue of selectively inactivating microorganisms while leaving the sensitive materials unharmed by manipulating and controlling with femtosecond laser systems.

Femtosecond laser treatment enhances DNA transfection efficiency in vivo

BackgroundGene therapy with plasmid DNA is emerging as a promising strategy for the treatment of many diseases. One of the major obstacles to such therapy is the poor transfection efficiency of DNA in vivo.MethodsIn this report, we employed a very low power, near-infrared femtosecond laser technique to enhance the transfection efficiency of intradermally and intratumorally administered DNA plasmid.ResultsWe found that femtosecond laser treatment can significantly enhance the delivery of DNA into the skin and into established tumors in mice. In addition, we found that both laser power density as well as duration of laser treatment are critical parameters for augmenting DNA transfection efficiency. The femtosecond laser technique employs a relatively unfocused laser beam that maximizes the transfected area, minimizes damage to tissue and simplifies its implementation.ConclusionThis femtosecond new laser technology represents a safe and innovative technology for enhancing DNA gene transfer in vivo.

Prospects for a novel ultrashort pulsed laser technology for pathogen inactivation

The threat of emerging pathogens and microbial drug resistance has spurred tremendous efforts to develop new and more effective antimicrobial strategies. Recently, a novel ultrashort pulsed (USP) laser technology has been developed that enables efficient and chemical-free inactivation of a wide spectrum of viral and bacterial pathogens. Such a technology circumvents the need to introduce potentially toxic chemicals and could permit safe and environmentally friendly pathogen reduction, with a multitude of possible applications including the sterilization of pharmaceuticals and blood products, and the generation of attenuated or inactivated vaccines.

Raman scattering studies of the low-frequency vibrational modes of bacteriophage M13 in water?observation of an axial torsion mode

Low-wavenumber (≤20 cm−1) acoustic vibrations of the M13 phage have been studied using Raman spectroscopy. The dominant acoustic vibrational mode has been found to be at 8.5 cm−1. The experimental results are compared with theoretical calculations based on an elastic continuum model and appropriate Raman selection rules derived from a bond polarizability model. The observed Raman mode has been shown to belong to one of the Raman-active axial torsion modes of the M13 phage protein coat. It is expected that the detection and characterization of this low-frequency vibrational mode can be used for applications in nanotechnology such as for monitoring the process of virus functionalization and self-assembly.

Selective inactivation of human immunodeficiency virus with subpicosecond near-infrared laser pulses

We demonstrate for the first time that human immunodeficiency virus (HIV) can be inactivated by irradiation with subpicosecond near-infrared laser pulses at a moderate laser power density. By comparing the threshold laser power density for the inactivation of HIV with those of human red blood cells and mouse dendritic cells, we conclude that it is plausible to use the ultrashort pulsed laser to selectively inactivate blood-borne pathogens such as HIV while leaving sensitive materials like human red blood cells unharmed. This finding has important implications in the development of a new laser technology for disinfection of viral pathogens in blood products and in the clinic.

Observation of the low frequency vibrational modes of bacteriophage M13 in water by Raman spectroscopy

BackgroundRecently, a technique which departs radically from conventional approaches has been proposed. This novel technique utilizes biological objects such as viruses as nano-templates for the fabrication of nanostructure elements. For example, rod-shaped viruses such as the M13 phage and tobacco mosaic virus have been successfully used as biological templates for the synthesis of semiconductor and metallic nanowires.Results and discussionLow wave number (≤ 20 cm-1) acoustic vibrations of the M13 phage have been studied using Raman spectroscopy. The experimental results are compared with theoretical calculations based on an elastic continuum model and appropriate Raman selection rules derived from a bond polarizability model. The observed Raman mode has been shown to belong to one of the Raman-active axial torsion modes of the M13 phage protein coat.ConclusionIt is expected that the detection and characterization of this low frequency vibrational mode can be used for applications in nanotechnology such as for monitoring the process of virus functionalization and self-assembly. For example, the differences in Raman spectra can be used to monitor the coating of virus with some other materials and nano-assembly process, such as attaching a carbon nanotube or quantum dots.